Photographic gelatin layer



irso STATES rATsNT o i-icEj rno'roGnArnIc GELATIN LAYER Johannes Brunken, Dessau in Anhalt, Germany,

v assignor to Agfa Ansco Corporation, Binghamton, N. Y., a corporation of New York 'No' Drawing.

Application February 10, 1933,

Serial No. 656,196, and in Germany February 4 Claims. (Cl. 95-7) My present invention relates to hardening of photographic gelatin layers.

One of its objects is a hardened photographic gelatin layer. Further objects'will be seen from the detailed specification following hereafter.

In my application Ser. No. 549,331 matured into Patent 1,870,354, I have described photographic gelatin layers hardened by means of dialdehydes.

According to this invention I have found that derivatives of the dialdehydes are very well suited for hardening photographic gelatin layers. These derivatives have at least one of their aldehyde groups substituted so as to correspond with 5 the following general formula wherein X represents hydrogen or the radical of an inorganic acid or an organic acid and Y represents the acid radical ofan inorganic acid or an organic acid. If X represents H and Y SOzNa there results the bisulfite compound of the alde-f hyde. If X and Y represent, for instance, Cl-IaIJO there results the tetra-acetate of the dialdehvde.

The hardening action of my new hardening agents is probably caused by the separation of free aldehyde from the derivatives enumerated. This is evidenced by the fact that the gelatin used must have a minimum pH value which is generally about pH=4 (gelatin as usually on the market has a value of pH=5 to 8) whenmeasured after the method disclosed by Tiidt in Chemikerzeitung 1927, pages 302 to 303. As the dialdehyde derivatives included in my invention can be easily saponified, gelatin of the value of pH=4 appears to be sufiicient to saponify part of the aldehyde derivative added which effects the hardening. The hardening action of the dialdehydederivatives becomes more intense with an increasing pH value of the gelatin used.

The hardening of photographic materials takes place in twostages. A first hardening efiect occurs after incorporating the hardening agent in the gelatin and, because in this stage there still remains undecomposed derivative a second hardening occurs in developing the exposed photographic material. This hardening in two stages has the advantage that they developer more easily penetrates 'the photographic layer though substantially the same hardening effect may be finally obtained as with the free dialdehydes. This is evidenced by thefollowing experiment.

When testing gelatin having incorporated glyoxal-sodiumbisulfite in water it will melt at 34 C. and when testing the same gelatin in a developer (containing 40 grams of potassium carbonate and 40 grams of sodium sulfite perliter) it will melt at 43 C.

The'protographic layers hardened with the aldehyde derivatives I disclosed show a good stability. Moreover, the aldehyde derivatives form solid substances and are more stable and easier to handle than are liquid aldehydes. The quantity of dialdehyde derivative added to the gelatin amounts to about 0.2 to 5 grams per 100 grams of gelatin, however, my invention is not limited to this range given rather for illustration. The most suitable amount can be easily determined by experiment. If too large quantities of hardening agent are added to the gelatin, the same may crystallize out and thus impair the finished layer. The addition of the hardening agent is made in form of. a solution preferably an aqueous solution. If the compoundis insoluble in water any solvent may be used which is sufficiently miscible with water, for instance, alcohol, methanol and acetone. The addition 80 is preferably made to the finished gelatin solution before being cast.

The following examples illustrate the invention:

Example 1.500 grams of a gelatino-silver- 8 halide emulsion containing about 90 to 100 grams of gelatin are mixed with 5 cc. of an aqueous solution of 10 per cent strength of glyoxal-sodiumbisulfite. Then the mixture is cast onto a support of glass or a film and dried. The layer obtained melts at 34 0., whereas the unhardened emulsion melts at 31 C.

Example 2.500 grams of a gelatinovsilverhalide emulsion containing about 90 to 100 grams of gelatin are 'mixed with 15 cc. of an alcoholic solution of 2 percent strength of glyoxal-tetraacetate and then cast. After drying the emulsion has a melting point0f 33 (3., whereas the unhardened emulsion melts at 31 C.

The invention is not limited to the foregoing examples nor to the specific details given therein. Other dialdehyde derivatives of the kind set forth herein may be used without departing from the scope of my invention.

What I claim is:

1. A photographic material provided with a gelatin layer containing besides the condensation product of gelatin with a dialdehyde, a substantial amount of aderivative of the dialdehyde, at least one of the aldehyde groups being substituted, so as to correspond with the formula.

OH- Y0 wherein X represents hydrogen or the radical of an organic or inorganic acid and Y represents the acid radical of an organic or inorganic acid. 3. A photographic material provided with a gelatin layer containing the condensation product of gelatin with glyoxal besides a substantial amount of glyoxal-sodiumbisulfite.

4.'A photographic material provided with a gelatin layer containing the condensation product of gelatin with glyoxal besides a substantial amount of glyoxal-tetra-acetate.

' J OHANNES BRUNKEN. 

